The Big '20mph Zone' Con

[Otta]

On both this thread and the one in the lounge people have said that a 20mph zone would "cause overtaking".

That is simply not true.

What "causes" overtaking is arseholes that think the rules don't apply to them and that they have the right to drive as fast as the bloody well like thank you very much.

[neilson99]

I'd be over the moon to ever get over 20mph on any roads in the area.

Anyone who thinks reducing speeds will reduce dangerous driving is an idiot.

I do agree Southwark Council are a completely ineffectual, self serving utter waste of time and money though!

[DulwichFox]

Whilst attempting to drive at <20 MPH I find myself constantly looking down at my speedo to check my speed

thus taking my eye off the road...

It is much easier to judge 30 MPH.... been doing it for 40 years

Just a thought.

DulwichFox

[mako]

Totally agree with you Dulwich Fox.

Otta anyone who has been driving in dulwich with the new 20s will i expect disagree with you. Even if the underlying cause is aresholes, the arseholes arent reduced by a change in limit, however they are more likely to try and overtake you at 20 than they would at 30 (as many have already reported) so the change IS caused by the change in limit.

[Lowlander]

DulwichFox Wrote:

-------------------------------------------------------

> Whilst attempting to drive at myself constantly looking down at my speedo to

> check my speed

> thus taking my eye off the road...

>

> It is much easier to judge 30 MPH.... been doing

> it for 40 years

>

> Just a thought.

>

> DulwichFox

Shouldn't take you too long to adjust. I can tell by engine noise alone when I'm doing 30.

[mako]

Rodney, my understanding is the money received from the speed cameras can be spent however the council chooses and doesnt necessarily go to the police to deal with their costs. so it can be revenue positive for the council and cost the police.

[DulwichFox]

Lowlander Wrote:

-------------------------------------------------------

> DulwichFox Wrote:

> --------------------------------------------------

> -----

> > Whilst attempting to drive at > myself constantly looking down at my speedo to

> > check my speed

> > thus taking my eye off the road...

> >

> > It is much easier to judge 30 MPH.... been

> doing

> > it for 40 years

> >

> > Just a thought.

> >

> > DulwichFox

>

> Shouldn't take you too long to adjust. I can tell

> by engine noise alone when I'm doing 30.

I drive an automatic and at those speeds 20 - 30 it does not make much noise..

If it was a manual then I would know what gear I was in..

Dulwichfox

[Otta]

mako Wrote:

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> Totally agree with you Dulwich Fox.

> Otta anyone who has been driving in dulwich with

> the new 20s will i expect disagree with you. Even

> if the underlying cause is aresholes, the

> arseholes arent reduced by a change in limit,

> however they are more likely to try and overtake

> you at 20 than they would at 30 (as many have

> already reported) so the change IS caused by the

> change in limit.

No it isn't. Nothing is making them take over except for their innate desire to go faster. It is them that is to blame, no speed limit has gotten in to their car and made them drive like arseholes.

[mako]

Its very simple otta. Before the change in limits there was less overtaking. changing the limit has resulted in more overtaking. It is therefore a cause of more overtaking. That doesnt take responsibility away from the driver and they may be to blame but why they overtake isnt as relevant as do they overtake in this debate.

[mako]

anyone who regularly drives will know that 'sunday drivers' are some of the very worst and least safe drivers yet they often drive slower than average. so 'arsehole' drivers' isnt just a speed debate.

[uncleglen]

20mph is a right pain in my car- in 3rd gear it sounds like I should be changing up but 4th gear is too high! Also observing commercial vehicles and buses around- they are ignoring the 20mph

[Heart108]

1. Could someone post a link to the traffic engineering argument behind the blanket 20mph? This is a huge decision for Southwark Council to have taken. Where and when was the debate/consultation/reasoning behind this decision? Who took it?

2. Could someone post a scientific link to back up the argument ( mentioned a couple of times on this forum) that driving at 20mph is more polluting/petrol consuming than 30mph?

3. Having written to to challenge elements of the recent Lordship Lane parking bays debate, I received an impressively detailed/reasoned email from Michael Herd - Network Development Officer answering specific points in my letter. ( I haven't had time to digest his email yet enough to agree/disagree with the points he made but in terms of reasoned accountability surely a 20MPH blanket borough policy deserves a similar statement from the Council and those behind the 20MPH Zone decision?)

* * *

I would like to read the science behind the 20MPH speed limit. I am amazed that I have never received anything through my front door ( SE22) nor been aware of any consultation. Has anyone else?

* * *

In the mean time, can someone answer this: how is it sensible to impose on a road as wide and free as Denmark Hill the same 20mph speed limit that you would impose on a highly populated residential side road with speed humps?

I defy those who took the decision to implement the 20mph speed limit everywhere to state categorically that it is not a hidden policy decision to intend to introduce speed cameras as a way of generating revenue for the borough rather than 20MPH limit being strictly necessary for safety and reduction of pollution.

[peckhamside]

I have not read every post so some of these points may have been made.

1. Driving more slowly saves fuel.

2. It is so much safer for all road users including cyclists and pedestrians because if another motorist makes a mistake everyone has more ti,e to stop/ avoid them etc.

I support 20 mph zone.

[bawdy-nan]

Here's a few links which collate the evidence:

http://www.rospa.com/about/currentcampaigns/publichealth/info/rs4-casestudy-20-mph-zones.pdf

http://www.dannydorling.org/wp-content/files/dannydorling_publication_id3924.pdf

http://www.tfl.gov.uk/cdn/static/cms/documents/research-summary-no2-20mph-zones.pdf

from the tfl report above:

Casualties

The impact on casualties due to the

introduction of 20 mph zones in London

can be summarised as follows;

● Allowing for background changes in

KSI casualty frequencies, the

installation of 20 mph zones has

reduced the frequency of road user

casualties within the zones by about

45% and reduced the frequency of

fatal or serious (KSI) casualties by

about 57%.

● There were statistically significant

reductions in the KSI casualty

frequency for most classes of road

user within the 20 mph zones.

● The KSI casualty frequency for

children also fell significantly --

by 60%.

● The severity ratio (the ratio of KSI

casualties to all casualties) fell from

0.16 to 0.12 following zone

installation ? indicating a reduced

severity.

● The average annual reduction in fatal

and serious (KSI) casualties per 20

mph zone suggests an annual saving

of about 66 KSI casualties across all

of London?s current 20 mph zones.

Using DfT figures this is equivalent to

a current annual saving of at least

?8.8 million, at 2001 prices.

Here's the 8 page thread where all of this was discussed last month http://www.eastdulwichforum.co.uk/forum/read.php?5,1459395,page=1

[mako]

Peckhamside. My cars manual says optimum speed for fuel consumption is 52mph. Slower speed certainly does not usually mean less fuel in fact the reverse is generally true until you reach this point when it declines.

Useful links bawdy but it ignores the fact that there has been a long term decline in all reported raod casulaties in the uk, the most recent full year data (2013) was the lowest ever number of deaths on record, close to 50% down in ten years. The 20mph limits were applied to the most dangerous roads where they were probably necessary (near schools etc) so to use this as a basis for expected improvements elsewhere is ridiculous, but that doesnt stop this council using it as if a fact that there will be a similar percentage improvments. Certainly its hard to reduce 57% of fatalities on roads where there are currently none.

[mako]

It also says that changing the limit on its own has had an irrelevant 1mph chamge on average speed and only speed humps and raised junctions actually made any difference to new 20mph zones. If this was a safety issue fom the council then we would be getting humps which work rather than cameras which dont but do raise cash.

[mako]

How can anyone who has more than the average ten year olds maths or logic skills accept the councils calculation that is based on the savings on the new 20 zones being the same as on the previously installed 20 zones. they quote that the 20mph zones being used as evidence had crash figures double that of all other 30mph roads before being made 20. Of course there were improvments to be made-these were the worst roads in london. You just cant apply that to sydenham hill for example and say that the same improvements will happen.

[Blah Blah]

Completely agree with all your points Mako and when tfl do publish the data for 2014 we can looks at the figures for Islington and the two other boroughs to see if and what difference a blanket 20mph limit made to their annual casualty figures.

Just on speed cameras. The council can't just erect speed cameras as they please and where they please. Speed cameras are not the same as cctv that is used for giving out parking tickets.

The DfT says that;

For selecting potential camera sites, it is recommended that analysis of collision data should be undertaken over a

minimum period (e.g. most recent 3 years, or preferably 5 years) to determine whether a camera is an appropriate

solution to reduce speeds and/or collisions at that site. Average (mean) and 85th percentile speeds should also be

collected so that the data is not more than 12 months old. This will help to demonstrate the level of non compliance

with the speed limit, which itself should also have been constant over the same minimum period.

The local partnership is fully accountable for these decisions and should be proactive in communicating information

on the deployment of cameras through the usual channels, including the Local Transport Plan process and local Speed

Management Strategies.

So clearly from that, the council has to wait at least three years and then have evidence and good cause for erecting speed cameras.

[Loz]

peckhamside Wrote:

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> I have not read every post so some of these points

> may have been made.

> 1. Driving more slowly saves fuel.

Not if you have to drop a gear. Petrol consumption is not governed by how fast you are going, but how much you have to depress the accelerator pedal. That's why you see cars advertised with "city cycle" and "highway cycle" MPGs, with the faster highway cycle usually having the higher MPG.

[uncleglen]

If you google fuel consumption vs speed graphs are there . Otherwise

http://www.myengineeringworld.net/2012/05/optimal-speed-for-minimum-fuel.html looks quite straightforward and it converts kph to mph

[wulfhound]

In the mean time, can someone answer this: how is it sensible to impose on a road as wide and free as Denmark Hill the same 20mph speed limit that you would impose on a highly populated residential side road with speed humps?

Because 20mph can be thought of as primarily about reducing the number and severity of casualities , and the overwhelming majority of injury collisions happen on the sort of roads which "common sense" would hold to be the 30 ones.

Denmark Hill (whole stretch from Herne Hill town centre to Camberwell) seems to average about 4 "serious" (per Stats19) collisions per year. The residential roads adjoining it? Practically zero. Whether 20mph is a good or effective tradeoff is debatable, but doing it on minor roads only has very little effect on the problem it's supposed to address.

You just cant apply that to sydenham hill for example and say that the same improvements will happen.

In percentage terms you probably can, but Sydenham Hill has a fairly good safety record for its type & so the absolute numbers won't be affected so much. Arguably the top bit of Sydenham Hill is plenty wide enough to put in good quality cycle lanes & leave the limit at 30 for other traffic, but I can see why a blanket limit is easier for people to understand.

[david_carnell]

DulwichFox Wrote:

-------------------------------------------------------

> Lowlander Wrote:

> --------------------------------------------------

> -----

> > DulwichFox Wrote:

> >

> --------------------------------------------------

>

> > -----

> > > Whilst attempting to drive at > > myself constantly looking down at my speedo

> to

> > > check my speed

> > > thus taking my eye off the road...

> > >

> > > It is much easier to judge 30 MPH.... been

> > doing

> > > it for 40 years

> > >

> > > Just a thought.

> > >

> > > DulwichFox

> >

> > Shouldn't take you too long to adjust. I can

> tell

> > by engine noise alone when I'm doing 30.

>

> I drive an automatic and at those speeds 20 - 30

> it does not make much noise..

>

> If it was a manual then I would know what gear I

> was in..

>

> Dulwichfox

Utter nonsense. The idea that you need to constantly check your speedo to maintain 20mph is simply an indication you're not a very good driver.

Check once, attain 20mph, then keep your foot in the same position and monitor speed through simple visual clues like: is stuff passing through my field of vision quicker than before?

[kford]

But one does, David, I tried it last night. You soon creep up to 25-27, especially in an auto with a quiet engine. I'd rather my concentration be spent on looking out for danger, don't you?

[Lowlander]

kford Wrote:

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> But one does, David, I tried it last night. You

> soon creep up to 25-27, especially in an auto with

> a quiet engine. I'd rather my concentration be

> spent on looking out for danger, don't you?

And I presume in 30 mph zones you drive around 35 - 37???

[Loz]

david_carnell Wrote:

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> Utter nonsense. The idea that you need to constantly check your speedo to maintain 20mph is

> simply an indication you're not a very good driver.

I'll bet good money that you cannot maintain a car speed between 18-22mph for one mile without looking at the speedo every 30 secs or so.